1. Field of the Invention
The present invention is related to an information adding apparatus and information adding method, capable of adding information to an image file, is also related to an information extracting apparatus and information extracting method, capable of extracting such information from an image file into which this information is added, and is further related to a computer-readable recording medium for recording thereon a computer program used to execute an information adding process operation and an information extracting process operation.
2. Description of the Prior Art
In conventional techniques for adding information to images, a portion of an original image is changed within a range where the changed image portion cannot be visibly discriminated, or recognized by human's visibility based upon the below-mentioned two facts, and then additional information is embedded into this changed original image:
(1). Presently available computers are capable of displaying very huge numbers of colors, namely 16 million colors.
(2). Since visibility of human eyes is not so sensitive, even when colors are slightly changed from original image displays, this color change cannot be visibly recognized, or discriminated from original colors by human eyes.
As a result, in the conventional technique for adding the information to the image, there is such a problem that the image display, or image representation into which the additional information has been embedded, or merged is changed from the display of the original image, although this color change cannot be visibly discriminated by human eyes.
Also, the conventional technique cannot be applied to simple images such as a black/white binary-coded image, since such a color change may be visibly recognized by human eyes.